Electrical apparatus and method



May 23, 1933. c. 1. MO-NEIL ELECTRICAL APPARATUS AND METHOD Fi1ed April 21, 1930 w Patented May 23, 1933 UNITED STATES PATENT OFFICE CHARLES I. KCNEIL, OI BLOOIFIELD, N'ETIT JERSEY, ASSIGNOB' '10 ECLIPSE AVIATION CORPORATION, OF EAST ORANGE, NEW JERSEY, A CORPORATION OF NEW JERSEY snowmen. arraaa'rus am) xn'mon Applicatiqzui filed April 21,

This invention relates to dynamo electric machines and one of the objects thereof is- ,to provide a novel method. for improving commutation in a dynamo electric machine 5' by'preventing sparking at the brushes.

' Another object of the invention is to providea novel method for im rovingv ommu-. tation in a variable s direct current dynamo electric machine by preventing 1o sparking at the brushes irrespective of the speed 0 the machine.

Another object is to rovide in a dynamo electric machine a novel arrangement of the magnetizing windings on commutating l6 poles so that the proper commutating pole strength may be had uponincreases in speed of the machine. i

Another object is to provide an ap aratus which will vary the magnetizing e ect of so the commutating le windings in accordance with variations in the main field strength resulting from variations in speed "in a dynamo electric machine.

Although but one embodiment onlyof the present. invention is illustrated in the accompanying drawing, it is to be expressly understood that the drawing' is for pur-, poses of illustration onl and are not designed as a definition o the limits of the invention, reference being bad for this purpose to the appended claims.

' Fig. 1 is a diagrammatic view showing one ofthe commutatin le windings in' series.

with the load an t e other commutatin pole winding in series with the shunt fiel Fig. 2 is a conventional representation of a four pole direct current machine, showing the relation of the magnetizing windings and embodyin the features of the invention.

As is well own to those skilled inthe art, upon increases in speed of direct currentdynamo-electric machines, the flux produced by. the armature reaction tends to shift the neutral point of the main field from its proper mechanical position. As a result a difference in potential exists between the commutator segments short circuited' by the brushes, causing a sparking, which deteriorates both the commutator and the brushes. If an auxiliary or commutating 1830. Serial No. 448,138.

field fiux is rovided equal to and opposing that set up the armature reaction it will nullify theistortive efiect on the neutral point of the main field. This commutating field is created by coils wound on pole pieces placed between the main field poles of the malchine and are commonly known as inter- The method proposed in the present invention for increasing the interpole flux with increases in speed is to provide first two means of interpole excitation which oppose each other and which at the normal minimum operating speed of the machine produce a net effective flux sufiicient to correct the effect of armature reaction at that speed. In the next step of the method, upon increase in speed, the voltage regulator decreases the'strength of the main field therebyweakening the commutating field while the interpole magnetic excitation of one source is maintained constant. In the third step of the'method the opposing interpole magnetic' excitationof the other source is decreased inversely proportional to increases in the speed of the machine givinga resultant efiective increased flux at increased speeds of the machine, to correct the effect of the weakened main field upon the commutating field.

' The novel arrangement of magnetizing windings and apparatus for carrying out I the process is disclosed in the drawing where A represents the frame of a four pole direct current shunt field dynamo electric machine. On the frame are mounted the four main field pole pieces B disposed at the roper. angle on the interior of the frame. Mi way between these main field poles are positioned the four commutating poles C commonly known and hereafter termed interpoles. Within the frame and between the poles an armature is adapted to rotate having a commutator D from which the current generated by the machine is col-- lected by the brushes E, F.

The. current collected from the commutator supplies a substantially constant load consuming device (not shown) by means of lead wires G and H. In series with one of mounted on each of the main field poles."

In series with this shunt field winding is a differential interpole winding K having coils K K K K of the required number, of turns on each of the interpoles wound or connected in such a manner as to create a magneto motiveforceopposing the magneto motive force of the coils 1 ,1 1,, L, which latter Main series with the load. These second coils K K K,, K, are so designed with respect to the coils I 1,, I L that a net effective flux is produced by coils 1., I 1,, L sufficient to correct the distortion of the neutral point of the main field caused by the armature reaction, when the machine is running at normal minimum operating speed.

.A voltage regulator is provided to maintain the voltage output o the machine constant by varying the main shunt field strength. This regulator is composed of a resistance Ii in series with the main field coil and the differential interpole winding K but under normal operating speed is short circuited by a switch M. This switch is of the vibrating contact type having a pivoted arm M of magnetic material connected at one end on one side of the resistance L and having a contact M on the other end adapted to cooperate with a contact M positioned on theother side of the resistance. A sprin M, holds these contacts closed. A coil N is connected across. the line that is responsive to voltage and constitutes an electro-magnet for attracting the arm against the action of the spring.

When the) machine is operating at a normal speed the magneto motive force of the differential interpole winding K opposes the magneto motive force of'the main interpole winding I and the design of the coils of the two windings is such that an effective flux is produced by the main interpole winding to correct the distortive effect of armature reaction at that speed. Upon an increase in speed the voltage output tends to increase at which time the voltage .coil N is sufficiently energized to open the short circuiting switch M and the resistance L is inserted in the shunt field circuit. The period of time during which the resistance. L is in the shunt field circuit varies with the speed. At a speed greaterthan normal the switch contact M will vibrate, and the" greater the increase in speed the greater will be the number of vibrations over a given period 'of time with the result that ,theresistance L is in the circuit a longer time producing an effective decrease in the field current and a substantially constant voltage. output is maintained.

'- With the load remaining substantially constant and the voltage output maintained constant the magneto-motive force produced by'the main interpole winding I will remain constant at any speed. The effective current in the shunt fieldcircuit is inversely proportional to the effective resistance in that circuit which, as explained, increases in' direct proportion with increases in speed. The magneto-motive force produced by the differential interpole winding K is therefore inversely proportional to the speed. As the magneto-motive force in the main interpole winding I remains substantially constant and the magneto-motive force in the differcntial-winding K decreases proportionally with increases in speed the net effect will be a resultant increase in the fiuxproduced by the main interpole winding I directly -proportional to the speed.

As is apparent, a. simple and effective means has been provided for increasing the effective interpole flux upon increases In speed of the dynamo-electric machine which will correct the distortive effect produced on the main shunt field by the .armature reaction and prevent sparking at the brushes.

It will be obvious that the invention is not limited to the specific form described and illustr ated in the drawing, but is ca able of a variety of. electro-mechanical em iments. Various changes, which will now appear to those skilled in the art, may be made in the form, details of construction and arrangement of parts without de arting from the spirit of the invention, an reference is therefore to be had to the appended claims for a definition .of the limits of the invention.

What is claimed is: Y 1. The. method of varyin the interpole flux with variations in spee of a dynamoelectric machine having a main inter ole winding in series with a load, and a di erential interpole winding in series with a shunt field, which consists in producing an opposing. magneto-motive force in each winding to give a proper resultant effective flux at normal operating speed of the machine, and then varying th magneto-motive force produced by one winding in ac cordance with variations in the speed of the machine to give a resultant increased effective flux upon an increase in speed of the machine. a

2. The method of varyin the interpole flux with variations in spee of -a dynamoelectric machine having a main interpole winding in serieswith a substantially constant load and a differential inte le winding in series with-the shunt fie d of said machine, which consists in equalizing the magneto-motive force produced by each 1 winding to give the proper efiective flux at pole flux with increases of speed of a dynamo-electric machine having a main inter ole winding and a difi'erential interpole win ing on the same pole piece located between the winding of the shunt field of said machine, which consists in producing a magneto-motive forcein each interpole winding to give the proper effective flux at normal minimum operating speed of the machine, of then machine, a load circuit, includin controlling the voltage. output of the machine, u on increases in speed, by decreasing the eld current, and then decreasing the magneto-motive force in oneinterpole windi in accordance with the decrease in the fi efid current to give a resultant increased interpole flux upon increases in speed.

A. The method of increasing the interpole flux with increases in speed of a dynamoelectric machine having a main interpole winding in series with a substantially constant load and a difierential interpole winding in series with a shunt field, which conforce opposing the magneto-motive force sists in producing a magneto-motive force in each wlnding to give the pro 'r efiective flux at normal'operating spec of the machine, of then maintaining the magnetomotive force of the main interpole winding constant upon increases in speed of the machine by decreasing the 'field'current, and

then decreasing the magneto-motive force in the difi'eren'tial winding by and in' accordance with the decrease in the field curfiux with an increase in speed of the machine. i

5. In combination with a dynamo-electric a main interpole winding and ashuntfie d circuit including a differential inter le winding, and means for. maintaining t e voltage in the load circuit constantand decreasing the current in the field circuit with increases in speed of the machine, whereby a resultant increase in the interpole flux will be pro"- duced upon increases in speed of the machine.

6. In combination with a dynamo-electric machine, a load circuit including a main interpole winding, a shunt field circuit ineluding a difierential interpole winding and means comprising a resistance and a voltage responsive circuit breaker for maintaining the voltage output of themachine constant by varying the field current to produce a resultant effective increased interpole flux upon increase'in speed.

7. In combination with a dynamo-electric machine, a constant load circuit including a main interpole winding for producing a magneticfield, a shunt field circuit includinga differential interpole windin for producing an opposing magnetic the machine for maintaining the main interpole'field constant and for varying the differential interpole ,field to give an efiective eld, and .means responslve to variations in speed of resultant interpole field, upon increases in 3? speed. v

I 8. In combination with a dynamo-electric machine having a shunt field circuit, a load circuit, means in the load circuit for producing an interpole magneto-motive force in r0 rtion to the load, means in the shunt e1 circuit for producing an opposing variable interpole magneto-motive force, and means interposed in the shunt field circuit for decreasin the opposing interpole magneto-motive orce upon an increase in speed of the machine .so that a resultant efiective interpole flux speed.

is produced with increases in 9. In combination with a dynamo-electric produced by the first named means, and means responsive to increases in speed for decreasing the ma eto-motive force roduced by thesecon named means to e ect a resultant increased interpole flux for increases in speed.

10. In combination with a dynamo-electric machine, a load circuit including means for roducin an interpole magneto-motive or roducing a variable interpole magnetomot1ve force opposing the magneto-motive force produced and means variable in proportion to variay the first named means, 7

u orce, a s unt field circuit including means no rent to give a resultant increased efiective f tions in speed for maintaining the current of the load circuit substantially constant and varying the current in the shunt field circuit to efiect a resultant interpole flux which increases in direct proportion to increases in speed 11. In combination with a dynamo-electric machine, .a constant load circuit, means in said load circuit for producing a ma1ninter-' pole magneto-motlve force, a shunt field circuit means in said shunt field, circuit for 1 producing a diflerential interpole magnetomotive force, means for maintaining the current in the load circuit substantially constant by varying the field current upon variations in speed of the machine so that an effective interpole flux is provided which varies directly with the speed.

12. In combination with a dynamoelectric machine, a load circuit including a main 5 windin for producing an interpole flux, a

shunt field circuit including a variable resistance and a differential Winding, the latter being adapted to produce an interpole magneto-motive force opposing the magneto- 1 motive force produced by the main Winding, a vibrating switch responsive to variations in speed for increasing the resistance in the shunt field circuit upon increases in speed of "the armature of said machine to maintain the magneto-motive force produced by the main winding constant and to decrease the magneto-motive force produced by the main Winding constant and to decrease the magneto-motive foice produced by the differentiel winding to effect c, resultant increased interpole flux for increases in speed.

in testimony whereof I have signed this specification. V.

i. McNElL. 

